U.S. Pat. No. 2,921,089 describes the use of dipropylheptyl phthalate and dipropylheptyl adipate as plasticizers for polyvinyl chloride (PVC) and cellulose acetate. The mixtures of these esters with PVC are said to feature good low-temperature flexibility properties.
U.S. Pat. No. 4,426,542 teaches the preparation of alcohol mixtures which comprise 2-propylheptanol and 2-propyl-4-methylhexanol, the use of these alcohol mixtures for the preparation of phthalic esters, and the use of these phthalic esters as plasticizers for PVC. The mixtures of these esters with PVC are said to have good low-temperature flexibility properties and low plasticizer volatility.
EP 366 089 discloses the preparation of alcohol mixtures which comprise 2-propylheptanol and other isomeric C10 alcohols, the use of these alcohol mixtures for the preparation of phthalic esters, and the use of these phthalic esters as plasticizers for PVC. The mixtures of these esters with PVC are said to have high electrical resistivity. They are moreover said to feature low plasticizer volatility and high resistance to kerosine-extraction of the plasticizer.
JP 4 104 740, JP 4 106 132. and JP 4 106 145 describe PVC foils with dipropylheptyl phthalate as plasticizer. These foils are said in particular to have good mechanical properties and to be capable of use in the agricultural sector and also in the construction sector.
JP 4 106 146 discloses plasticized PVC compositions with dipropylheptyl phthalate as plasticizer, where the plasticizer has low volatility and high resistance to oil-extraction, and the compositions can be used as cable sheathing.
The subject matter of JP 4 299 924 is PVC coatings for acrylic polymers with dipropylheptyl phthalate as plasticizer, these being resistant to soiling and capable of use in the agricultural sector.
According to JP 4 258 641, PVC coatings with dipropylheptyl phthalate and epoxidized 1,2-polybutadiene as plasticizer feature very good weathering resistance.
JP 5 194 761 and JP 5 194 810 relate to the production of coatings from PVC and phthalic esters which can be prepared from alcohol mixtures comprising 2-propylheptanol and 2-propyl-4-methylhexanol. The coatings are said to resist soiling and to be water-resistant.
JP 5 214 159 and JP 5 214 192 concern compositions composed of PVC and of plasticizer esters which can be prepared from alcohol mixtures comprising 2-propylheptanol, 2-propyl-4-methylhexanol, and 2-methyl-2-ethylheptanol. The compositions are said to be relatively resistant to oil and to water and to have only a slight tendency toward plasticizer exudation.
JP 5 339 388 and JP 6 002 281 describe PVC foils and PVC synthetic leather which comprise phthalates whose preparation was based on alcohol mixtures composed of 2-propylheptanol and 2-propyl-4-methylhexanol. The good low-temperature flexibility properties of these PVC foils are emphasized in that specification.
JP 6 001 858, JP 6 001 862, JP 6 001 900, and JP 6 001 901 describe plasticized PVC compositions with phthalates whose preparation was based on alcohol mixtures composed of 2-propylheptanol and 2-propyl-4-methylhexanol. These compositions can be used for the coating of umbrellas, tents, or rainproof jackets, for cable sheathing, and also for the production of interior trim for buildings and automobiles.
JP 7 157 615 discloses plasticized PVC compositions with plasticizer mixtures which comprise esters based on the alcohols 2-propylheptanol and 2-propyl-4-methylhexanol. Alongside the good low-temperature flexibility properties of these compositions, mention is made of the low volatility of the plasticizer in these compositions.
JP 7 173 356 describes plasticized PVC compositions with phthalates based on the alcohols 2-propylheptanol and 2-propyl-4-methylhexanol, with high electrical resistance, which can be used as cable sheathing.
JP 7 179 699, JP 8 034 891, JP 8 059 937, and JP 8 283 510 relate to plasticized PVC coatings with phthalates based on the alcohols 2-propylheptanol and 2-propyl-4-methylhexanol, which can be used for the production of floorcoverings, interior decoration, baby pants, shower curtains, and also printed packaging foils.
JP 8 157 422 describes phthalic esters with mixtures composed of aliphatic C9, C10, and C11 alcohols in which the alcohols present comprise 2-propylheptanol and 2-propyl-4-methylhexanol, and their use as plasticizers for the production of compounded plasticized PVC materials with good stability at high and low temperatures.
JP 8 301 295 describes plasticized PVC foils with esters based on the alcohols 2-propylheptanol and 2-propyl-4-methylhexanol, and their use for the production of flexible containers for the transport of synthetic resins.
JP 7 304 920, JP 7 304 921, JP 7 304 922, and JP 8 003 401 disclose plasticized PVC pastes with dipropylheptyl phthalate which feature good storage stability and can be used as plastisols, for example in the production of sealing compositions for the automotive industry.
Since August 2004, the applicant has been offering for sale the product Palatinol® 7PHP in the USA, this being a plasticizer mixture composed mainly of linear diheptyl phthalate and dipropylheptyl phthalate, and in this connection the applicant published the technical datasheet “Palatinol® 7PHP—General Purpose Phthalate” in August 2004.
Plasticizers based on 2-propylheptanol, in particular bis-2-propylheptyl phthalate, have a number of advantageous properties. When compared with other plasticizers using C10 alcohols, e.g. diisodecyl phthalate (DIDP)—prepared via trimerization of propene to give nonene mixtures and their subsequent hydroformylation, hydrogenation, and esterification—they also feature lower volatility at relatively high temperatures and better weathering resistance, properties which result in particular interest in plasticizers based on 2-propylheptanol for applications in the cable sector and for interior automobile trim, and also for outdoor use, e.g. for roof coverings and coated tarpaulins. However, other than in niche applications, plasticizers based on 2-propylheptanol have not been able to achieve any great penetration of the market. The main reason for this is the low level of gelling action of plasticizers based on 2-propylheptanol, which makes it more difficult for the user to produce plastified PVC mixtures with these plasticizers.
The gelling action of esters for PVC is mainly characterized via the solution temperature of the ester for PVC, and this can be determined to DIN 53408. The plasticizing action of esters is primarily based on their physical capability to dissolve PVC, in particular at elevated temperatures. The temperature at which the polymer is a clear solution in a particular ester is therefore an important criterion for its usefulness. The lower the solution temperature of the ester for PVC, the better the gelling action. Low solution temperatures permit use of low temperatures during the production and processing of mixtures composed of PVC and ester.
To circumvent these processing problems caused by unfavorable gelling performance of the plasticizer, other esters known as “fast fusers” which have very good gelling performance are added to these plasticizers, particular esters being those of lower alcohols, e.g. dibutyl phthalate or diisobutyl phthalate. Although addition of these fast fusers improves gelling performance, it impairs the properties of the plastic plasticized with this mixture, for example its cold-crack temperature and torsional stiffness, and the evaporation rate of the plasticizer out of the plasticized plastic is increased, leading to undesired phenomena, such as greater fogging and premature embrittlement, during the use of the plastics thus plasticized. Another disadvantage of the fast fusers mentioned is that, because their volatility is relatively high, complicated precautions have to be taken during their processing, to keep their workplace concentration low.
Because the application-related effects described above of plasticizers and of fast fusers are negatively correlated, so that when a mixture composed of plasticizer and fast fuser is used, although the gelling performance of the mixture is improved over that of the pure plasticizer, the advantageous application-related properties of the pure plasticizer are adversely affected to the extent that it is supplemented with a fast fuser, it was an object of the present invention to provide ester mixtures based on the plasticizer alcohol 2-propylheptanol where the gelling performance of the mixtures is improved more than proportionally via addition of esters of another alcohol, in relation to the amount added of the esters of the other alcohol, without more-than-proportional impairment of the other application-related properties of the ester mixtures based on 2-propylheptanol, e.g. cold-crack temperature, torsional stiffness, or volatility from foils. Ideally, the advantageous application-related properties of the ester mixtures based on 2-propylheptanol should be very substantially retained.